The operation of machinery in dusty environments can present challenges. One such challenge is protection of machine bearings from effects of dust and debris. Off-highway trucks, for example, are especially susceptible to bearing contamination due to the presence of high concentrations of dirt, water, and other contaminants in the working environment of the trucks.
One bearing type that is susceptible to contamination is the bearing arrangement located in the pinned joints attaching struts and similar components to the truck frame. One reason for this vulnerability is that the strut connects to the frame with an open structure that permits movement of the strut in the joint. One such structure includes a spherical-type bearing.
Spherical-type bearings or joints are commonly used in suspension systems to couple a shock or strut to a part of the machine, such as a control arm, in a fashion that allows the shock or strut to pivot or rotate around one or more axes relative to the control arm. In order to function properly over their service life, spherical bearings may be lubricated and efforts are made to minimize the amount of debris that enters the bearing and collects on internal surfaces, particularly those internal bearing surfaces that rub against one another as the bearing operates. Some spherical bearings types do not require lubrication. In those bearing types, preventing debris from coming into contact with internal bearing and joint surfaces becomes even more important because there is no fluid to contain and remove the debris.
To maintain the operational state of the bearing and minimize the amount of debris that enters the bearing, various attempts have been made in the past to seal the bearing. Some past solutions include bearing seals that entail seating a relatively small lip seal in the outer race of the bearing so that the seal rides on the ball or inner race as the bearing operates. However, in order to seat within the outer race, the lip seal must be relatively small, which tends to reduce the effectiveness of the seal. Moreover, such seals tend to fall off the edge of the ball or inner race and become crushed when the pin of the bearing moves into a maximum rotational position.
Other past solutions provide a type of flexible covering or boot over the entire bearing. Although such a covering may reduce the amount of debris that enters the bearing, it generally does effectively retain the lubrication within the internal structures of the bearing. Moreover, such a covering may not be appropriate for certain applications and may make visual inspections, repair, and routine maintenance of the bearing more difficult. In addition, in order to properly seal the bearing, such coverings or boots are often assembled tightly around one or more parts of the bearing and/or the components coupled to the bearing. If the different components to which the boot is coupled move relative to one another, particularly if they rotate relative to one another, the tight fit of the boot against each component causes different portions of the boot to move relative to one another, which may cause the boot to twist or wrap up and become damaged.
In pinned joints with spherical-type bearings, the strut can move in the joint along the pitch direction, where the strut pivots in a plane normal to the axis of the pin. The strut may also move in the yaw and roll directions in addition to pitch. The misalignment of parts produced by movement in the yaw and roll directions, in particular, requires the provision of a changeable gap between the strut and the support structure to which it is attached. It can be difficult to prevent contamination from entering through the gap, into the joint, and into a bearing supporting the strut on the frame.
It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some respects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.